African Eve Gets Lost in the 'Trees.' (Mitochondrial DNA Research)

African Eve Gets Lost in the 'Trees.' (Mitochondrial DNA Research)

Since 1987, an influential group of molecular biologists has published several reports indicating that analyses of mitochondrial DNA -- genetic material located outside the cell nucleus and inherited only from the mother -- track the maternal lineage of all humans back to one or possibly several women who lived in Africa around 200,000 years ago (SN: 9/28/91, p.197). That controversial contention gets the statistical rug pulled out from under it in two reanalyses of the most extensive sample of mitochondrial DNA studied earlier. The new findings appear in Feb. 7 SCIENCE.

One study, directed by S. Blair Hedges of Pennsylvania State University in University Park, builds five mitochondrial DNA trees but fails to pinpoint statistically the geographic origins of humanity. Particular sequences of chemical components of mitochondrial DNA appear about as often in all geographically separated populations, Hedges' team argues. This, they say, suggests that widely separated human groups have shared, or conserved, specific chemical arrangements of mitochondrial DNA since those populations diverged from a single group. Analyses of DNA sequences from within the cell nucleus may offer a better possibility of establishing a valid evolutionary tree for humanity, the scientists hold. …

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